A reactor is one of the components of a circuit that performs a voltage step-up or step-down operation. Patent Literatures 1 and 2 disclose a reactor used for a converter mounted on a vehicle such as a hybrid vehicle. The reactor includes, for example: a coil having a pair of coil elements; an annular magnetic core at which the coil is disposed and which forms a closed magnetic path; a case storing a combined product made up of the coil and the magnetic core; and a sealing resin (secondary resin portion, potting resin) packed in the case.
When the coil generates heat upon energization, the loss of the reactor becomes great because of the heat. Accordingly, in general, the reactor is used as being fixed to an installation target such as a cooling base such that the coil can be cooled. Further, it is discussed to dispose a sensor for measuring the physical quantity such as temperatures or current at the place near the reactor when the reactor is used, to control current or the like supplied to the coil in accordance with the measured temperature or current, for example. Patent Literature 1 discloses disposition of a current sensor at the magnetic core. Patent Literature 2 discloses disposition of a temperature sensor between the coil elements.